Flight simulation is a method of training aircraft personnel. In a simulator a trainee is placed in a realistically recreated aircraft environment designed such that the trainee, without leaving the ground feels he is in and operating an actual aircraft. An important element used to create this realism is a visual system which provides the trainee with an out-of-the-window scene which varies with his operation of the flight control system of the simulator, in a manner which corresponds to conditions encountered in actual flight.
During actual flight operations, for example, a pilot will manipulate the aircraft controls and thereby provide control signals to operate the control surfaces (rudder, flaps, etc.). As this process occurs, the pilot will view a change in the visual scene that corresponds, in the general case, to linear aircraft motion (altitude, course, and drift) and rotational aircraft motion (elevation or pitch, roll, and azimuth or heading). Accurate simulation requires reproduction of this correspondence between manipulations of the controls and changes in visual scene.
One method devised to effect this desired reproduction employs a camera model visual display system, hereinafter referred to as a visual system. A visual system may comprise a scaled-down model board of a typical landscape area such as an airport and the territory surrounding it. A typical model board used in flight simulation, mounted vertically, may measure 70 to 80 feet in length and 20 to 40 feet in height. Such model boards may cost upwards of one half million dollars and require an expensive bank of lights to provide uniform illumination across the model board.
The visual system also includes an optical probe that is directed at the model board and a camera attached to the optical probe. The picture taken by the camera is transmitted through a closed circuit to a display. In this manner the trainee is typically provided with a front windshield or straight-ahead view.
In order to simulate linear aircraft motion, the optical probe and camera assembly is positioned on a moveable gantry. Altitude is simulated by movement of this assembly toward and away from the model board. The simulated course is varied by vertical movement of this assembly up and down the model board. Drift or forward motion is simulated by movement of this assembly along horizontal tracks parallel to the model board.
In order to simulate rotational aircraft motion, the optical probe is provided with a pitch entrance prism, a rotational or dove prism, and an azimuth assembly. Elevation is simulated by tilting the pitch entrance prism. The simulated roll is provided by rotation of the dove prism. Azimuth or heading is simulated by movement of the azimuth assembly, which functions to rotate the camera and optical probe combination.
The prior art visual system described so far comprises a model board, a moveable optical probe and camera, and a display. A computer system is also provided in the visual system. The computer system receives inputs responsive to the trainee's manipulations of the aircraft controls. The computer system then controls the various movements of the optical probe and camera in order to change the trainee's view.
Prior art visual systems as described above are discussed in detail in U.S. Pat. Nos. 3,603,726 and 3,052,753. These visual systems provide the trainee with only an approximately 90.degree. field of view which corresponds to a front windshield view. An enlarged field of view e.g., a combined front and side windshield view extending over an approximately 120.degree. field of view can not be provided by existing single probe visual systems without unacceptable sacrifices in image clarity, resolution and perspective. In actual flight, however, simultaneous front and side views must be provided in order to determine such matters as the speed of the aircraft, turning points, and altitude during low flight maneuvers. Additionally, the pilot must have a combined front and side view to determine clearance when flying nap of the earth.
One way that existing simulators provide an enlarged field of view is by duplicating a visual system in its entirety. Hence, front and side views are provided by a dual visual system that comprises two identical model boards, two optical probes, two cameras, two gantrys, two banks of lights, and two computer systems, etc.
The advantages provided by such a dual visual system are, however, seriously offset by the undesirability of having to double every element in a visual system. For example, the costs of a visual system tend to become very high due to the double expense in providing two model boards, two gantrys, etc. Duplication also increases maintenance costs while doubling the mean time required to correct failures in system components.
The present invention provides a visual system that addresses the cited problems and improves upon the prior art visual systems by providing an enlarged field of view covering both front and side views with a single probe while preserving image clarity and high resolution. The present invention allows the construction of a visual system that is significantly less costly than the existing two probe, two model board systems.
With the apparatus of the present invention, only one optical probe must be positioned on one gantry in front of one model board, in order to provide the trainee with both a front and side view.